Potentially optimal body size to adjust tube current for individualized radiation dose control in retrospective ECG-triggered 256-slice CT coronary angiography.

INTRODUCTION We aimed to determine a potentially optimal body size index for adjusting the tube current in retrospective ECG-triggered helical 256-slice CT coronary angiography (CTCA) for individualized radiation dose control. METHODS Consecutive patients (n=102) with suspected coronary artery disease underwent retrospective ECG-triggered CTCA with a 256-slice CT scanner. Body mass index (BMI), nipple level (NL) bust and six anthropometric body size indexes, including thoracic anteroposterior diameter at NL, chest circumference (CC) at NL, left main (LM) and right coronary artery (RCA) origin level, chest area (CAr) and chest attenuation (CAt) at RCA origin level were measured, and their correlation with image noise in the aorta was evaluated using linear regression. Pearson correlation analysis was performed respectively to determine the body size index that correlated best with the other body size indexes. An equation was derived to use the best correlated body size index for adjusting tube current. RESULTS Linear regression demonstrated that CCRCA had the best correlation with image noise. Pearson correlation analysis showed that CCNL, CCLM and CArRCA had the closest linear relationship with CCRCA. The equations connecting CCRCA and tube current for males and females were XmA = 662 × (0.055 × CCRCA - 28.594) / 302 and XmA = 662 × (0.049 × CCRCA - 21.584) / 302, respectively, for a fixed image noise value of 30 HU. CONCLUSIONS Tube current selection is different for males and females, particularly in patients with a small chest circumference. CCRCA is an ideal body index for appropriately adjusting tube current in CTCA for individualized radiation dose control.